Turkish President Recep Tayyip Erdogan said Monday he proposed, to the U.S. and Russia, the setting up of a no-fly zone in northern Syria, after Ankara-backed fighters pushed the Islamic State group from the border area.

A U.N. investigation has established that President Bashar Assad's forces carried out at least two chemical attacks in Syria and that Islamic State jihadists used mustard gas as a weapon, according to a report seen by Agence France Presse on Wednesday.

The panel was able to identify the perpetrators of three chemical attacks carried out in 2014 and 2015, but was unable to draw conclusions in the other six cases that it has been investigating over the past year.

Turkish tanks and hundreds of opposition fighters thrust deep inside Syrian territory Wednesday in a lightning operation that within hours ousted Islamic State jihadists from a key Syrian border town.

The air and ground offensive -- the most ambitious launched by Ankara in the Syria conflict -- made rapid progress towards Jarabulus with rebel fighters already proclaiming victory by the late afternoon just 14 hours after it started.